TR chamber dimensions problem?

[karen]

Last year there were thousands of problems when primers started popping out. That had a different cause . . .

Um what was the cause? If you know then I know someone who might be interested in hearing what it was

Love

Karen

[rox]

The stickering test is no longer done with an inked bullet. An OAL guage with a real .308" bullet

Well I suppose that is a step forward, but...

if it is under limit (2.800") the rifle fails.

This suggests that factory ammo loaded to 2.8" OAL with the same bullet shape as used in the test might actually be able to contact the rifling of a rifle which passed the test! Furthermore, unless a bullet is specifically and carefully selected which is at the extreme of the range of variance in the ogive to meplat dimension (where significant variance can and does occur), the results could be even more skewed. And after it has been used a few times, unless replaced, the soft copper is likely to be deformed, potentially further skewing the test. As described it sounds flawed.

..

[rox]

Um what was the cause? If you know then I know someone who might be interested in hearing what it was

Was it not confirmed as being metallurgy? The problem was definitely occurring with generous chambers and ammo that was kept well below ambient temperature, so while the cause might not be known with certainty (I understand that metallurgical analysis was not performed within a desirable timeframe, if at all at this stage) I would think that chamber size could have been eliminated with reasonable confidence.

Regardless of the cause, I was trying to illustrate a point that the absence of a catastrophic failure to date does not mean that there is no possibility of a potential problem when multiple variables combine towards an extreme.

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[IainWR]

Remember that Rule 150 is a COMPETITION rule. The relevant safety rule is the one that says that the firer is responsible for the safety of his rifle and ammunition in combination (Rule 115). Also refer rule 151c which says that issued ammo in NRA TR competitions will correspond to CIP dimensions for Win .308" and will develop a Max Average Working Pressure of 3650 bar under CIP test conditions and that competitors are responsible for ensuring that their rifle is safe to use with such ammunition.

[karen]

Regardless of the cause, I was trying to illustrate a point that the absence of a catastrophic failure to date does not mean that there is no possibility of a potential problem when multiple variables combine towards an extreme.

I take your point but the only way of ensuring that there is no possibility of a potential problem when multiple variables combine towards an extreme is to not shoot at all. All we can do is to minimise the risk to as near zero as possible which in my opinion I would say is pretty much what has happened.

There has been talk of "rogue rounds" from certain quarters using a 20 year old example of an ammo malfunction using ammo which we don't use (only used once I think) which was completely irrelevant to the discussion to "prove" that a "rogue round" is a possibility. Now I'm not a statistician but even I could see that was a red herring!

As I said before, DON'T WORRY it's all under control and I am sure there will be more info in due course.

Love

Karen

[zanes]

I'm not sure when a .308 is working at pressures in the region of 60kpsi assurances such as "not had any problems to date" or "it's probably not an issue" really cut the mustard, so to speak (not having a pop at anyone/the NRA, just making a point.

[rox]

All we can do is to minimise the risk to as near zero as possible which in my opinion I would say is pretty much what has happened.

There has been talk of "rogue rounds" from certain quarters using a 20 year old example of an ammo malfunction using ammo which we don't use (only used once I think) which was completely irrelevant to the discussion to "prove" that a "rogue round" is a possibility. Now I'm not a statistician but even I could see that was a red herring!

As I said before, DON'T WORRY it's all under control and I am sure there will be more info in due course.

Thanks for all your replies – I am certainly not worried at all, and just want to fully understand the relevant rules (and a little of the history) to ensure compliance, safety and most of all to be able to carry on enjoying my shooting (which I hope you are)!

Of course we are talking about risk, which is an analogue variable. I know the history of that incident and knew the chap concerned in my youth, (met him again for the first time since the incident a few years ago). I have encountered one defective RUAG round (I won't say 'rogue'). It felt strange going-in so I unloaded to get a receiver full of powder. I suspect that it was due to a round which jammed due to excess bullet runout rather than being over-length, but I'll never know for sure, nor will we know what would have happened if I fired it. Probably nothing more than just another V Bull which is all I've experienced with high runout rounds since then.

I do feel that since rule 150 is effectively the embodiment of the proof house memorandum on reduced dimensions it is a bit crass to say it is a 'competition rule' not a 'safety rule' - after all, the proof house isn't concerned in the slightest with competition, and while folks are motivated to reduce dimensions to achieve a competitive advantage, the minimums (reduced or otherwise) exist to prevent them from creating an unsafe condition.

Good shooting and have fun!
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[Gaz]

Um what was the cause? If you know then I know someone who might be interested in hearing what it was

Was it not confirmed as being metallurgy? The problem was definitely occurring with generous chambers and ammo that was kept well below ambient temperature, so while the cause might not be known with certainty (I understand that metallurgical analysis was not performed within a desirable timeframe, if at all at this stage) I would think that chamber size could have been eliminated with reasonable confidence.

Regardless of the cause, I was trying to illustrate a point that the absence of a catastrophic failure to date does not mean that there is no possibility of a potential problem when multiple variables combine towards an extreme.

..

"Vivacious" loads from the factory was the reason I was told. Apparently it was a combination of high ambient temperatures and a load on the hotter side of the permitted envelope which caused primers to start popping.

Didn't see any problems with my rifle, but experienced quite a few as a RO during last year's meeting.

[rox]

"Vivacious" loads from the factory was the reason I was told. Apparently it was a combination of high ambient temperatures and a load on the hotter side of the permitted envelope which caused primers to start popping.

I find this a little hard to believe as the sole or primary cause when RWS brass can usually be pushed to much higher pressures than used in regular TR ammo, there was no other immediately apparent evidence of high pressure, and since primers were popping with ammo that was kept very cool indeed (using cool packs, chilled water bottles etc) until the moment it was chambered then fired quickly.

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[dromia]

Just for completeness in relation to the Rule 150 discussion.

From Robin Pizer, 1 Forest Corner, Liss Forest, Hampshire, GU33 7RA

28March 2014

Ongoing concerns

In the last six months, it has become clear that the technical advice, that the NRA trustees have received since 1999 regarding Rule 150, has not complied with the British Proof Authority Memorandum of June 1999 which permitted reductions in certain CIP specified dimensions for .308 Winchester chamber and barrel dimensions.

This 1999 Memorandum permitted

a reduced throat diameter
introduced in Rule 150 in 2000,

a reduced bore diameter
not introduced in Rule 150 until 2010,

a reduced groove diameter
not introduced in Rule 150 until 2010,

in rifles with these reduced dimensions only ammunition that does not exceed an average pressure of 3650 bar under CIP test conditions may be used.

It did not permit

a reduction in the length of the leade
introduced in Rule 150 from 2000 to 2006,

a reduction in the length of the throat
introduced in Rule 150 from 2007,

a reduction in freebore (or jump)
the NRA of Australia recommended 30 thou in Jan 1998.
specified as 25 thou in the RUAG contract in Jan 2010 but not included in Rule 150.

On 11 December 2013 the Proof Masters relayed to the NRA Trustees that they wanted gauges to check compliance with the Memorandum of June 1999 and to this end required the NRA to define a freebore (or jump). They were willing to accept a transitionary period in which they did not have gauges but in which they would require extra assurance from the gunsmiths concerning the accuracy of their declarations re G1
(throat dimension), F (bore dimension) and Z (groove dimension). They would then mark the rifles with a new Proof Mark indicating compliance with a revised Memorandum incorporating the freebore measurement. This would then warn owners of such rifles that only specified .308 Winchester commercial ammunition would be suitable for use in these rifles. The alternative was to withdraw the 1999 Memorandum and insist that all Target Rifles were fully compliant with CIP dimensions.

On 8 Feb 2014 I listened to one of our technical experts trying to explain to General Council how a short leade was compatible with the 1999 Memorandum. He acknowledged that he had provided expert technical advice in 2000 and 2007 which led to the changes to Rule 150. In 2010 he advised Jeremy Staples on the technical specification in the RUAG contract despite it being incompatible with Rule 150.

I cannot accept that John de Havilland would have agreed to the 2000 changes to Rule 150 had he been properly informed. John Jackman has confirmed he was not informed in 2007 and believes the matter was dealt with at a lower level as it was purely technical. Bill Richards has no recollection of any discussion or hearing the phrase 'short throat' before but points out it is nearly 5 years since he retired as chairman.

Julian Hartwell and Dick Horrocks were respectively vice chairmen of Council and of General Council in the interregnum after John Jackman retired and before Bill Richards was appointed. Dick commented 'I was not aware of any deviation of Rule 150 from the British proof memo of 1999. I assume that by "short throat", you are referring to "jump" (or distance between bullet ogive and land) and that the current Rule 150 referring to paragraph starting "the minimum throat length....." is the "deviation" from the 1999 agreement. The "bullet not touching" reference has always surprised me since while the NRA armoury method of inserting a blackened cartridge into a member's chamber measures only a "non touching" condition, standard hand loading practice advises a minimum jump of no less than 20 thou. In my latter years as a member of the Shooting Committee, the inadequacy of the current method was often discussed and the promise of a trial with gauges was made but never fulfilled.'

I certainly was not informed in February 2009, when I became NRA chairman, that Rule 150 was not compliant with the 1999 Memorandum. Neither was I explicitly informed of the major differences between the RUAG contract and Rule 150 in January 2010.
In August 2013, it became apparent to me that the Council was getting poor advice over Rule 150. Subsequently I met the London Proof Master in November 2013 to see the set of gauges they used to check CIP standard .308 Winchester rifles. He unexpectedly mentioned to me the jump declared by one gunsmith which happened to be substantially less than 25 thou.

In December 2013 I met the Birmingham Proof Master at his request because John Bloomfield had suggested to him that the Proof Houses did not need gauges to check the non standard features of rifles subject to the 1999 Memorandum. Given what the Proof Master said to me, any chairman would have carried out that visit. I did not accept John Webster's advice not to attend the meeting. If he had told me that for 14 years, NRA Rule 150 had not complied with the 1999 Memorandum, I would have required an explanation before attending. At the meeting the Proof Master said he had been naive in 1999 to trust the NRA to carry out their side of a gentleman's agreement to check compliance with the reduced dimensions permitted in the 1999 Memorandum. The NRA allowed the gunsmiths to self certify their own work.

I understand that the Birmingham Proof Master confirmed to John Carmichael on 6 Feb 2014 that he has not endorsed the clause in Rule 150 concerning the shortening of the throat length and would have insisted that it be incorporated into a revised Memorandum and would have required a consensus of agreement from members of the Pressure Trials Consortium. So the NRA had no authority to make that change and was foolish to do so.

Over the years since 1999, John Carmichael has repeatedly raised the issue of rifles not complying with Rule 150 but his efforts to get the issue resolved were batted into the long grass. On 8 Feb 2014 Tony Clayton made a very interesting remark:
It was something along the lines that there were many occasions of pulled bullets during his period as CRO on Century and the user of the rifle was told to get the rifle checked. So what happened to all these rifles ? Who checked them ?

At the General Council Meeting on 1 March 2014 John Kynoch is said to have raised this issue in respect of
an attempt at the Shooting Committee Meeting in May 2009 to get all rifles rechecked and new stickers attached in 2010 as a result of the introduction of the RUAG ammunition in summer 2009.
One notes how over a two year period ending in May 2011, a proposal to have all rifles rechecked got watered down in stages to a percentage and then just a random check under the control of the Shooting Committee.

On 8 Feb 2014 I urged the setting up of an independent inquiry into the failures of the NRA to comply with the British Proof Authority Memorandum of June 1999

by including the short leade condition in Rule 150 in 2000,

replacing it by the short throat condition in 2007,

whether RUAG were told or not about the short throat condition in 2010,

why the 25 thou jump was not added to Rule 150 in 2010.

It appears to me that there has been a major failure by those technical expert(s) that the Shooting Committee and Council have relied on over the last 14 years. One wonders if they are insured for giving bad advice.

It may be very difficult to set up an independent inquiry using NRA members due to the various gunsmiths that the members use who are in one camp or the other. So I urge very careful consideration is given to how this can be achieved. I am concerned that if one of these rifles causes an accident, the NRA Council and their technical advisers will be in the firing line.